faucet stem does not screw off

I am trying to remove a faucet stem from the shower faucet. It is a sterling. I used a wrench to fit over the nut and turned counterclockwise and it was so tight that I bent the nut.And now I cannot screw the packing nut back in Is there a way to just break the nut since I am replacing the shole stem and seat anyway? Or can I try wd40? thanks